1. Technical Field
The present disclosure relates to devices and methods for the replacement of joints, and more particularly, to patient-specific knee replacement devices, including methods of manufacturing and using such devices for achieving accurate resection of patient bones and accurate placement of prosthetics based on computer generated imaging of a patient.
2. Background of the Invention
One known method of treating knee and other joints with arthritis and other medical conditions is to replace surfaces of articulating joints with prosthetic devices through surgical procedures. It is critical that such prosthetic devices are accurately designed and manufactured and that they are installed correctly so that they relieve pain and provide an effective treatment method for such ailments. An orthopedic surgeon performing such joint replacement on a patient seeks to ensure, through surgery, adequate placement of the prosthetic and proper reconstruction of the joint being replaced. A particular patient's bone structure symmetry is one important consideration that a surgeon must consider when performing joint replacement surgery. Additionally, malposition of joint replacement prosthetics can result in untoward pain or premature wear of the bearing surfaces, which may require additional surgeries to correct. Improperly sized prosthetic components that are tool large or too small may also cause pain, loosening of prostheses or accelerated wear. Repairing improperly sized prosthetic components may require additional surgeries.
In the case of a knee, the condition of the patient's joint may require a partial or total replacement. A partial knee replacement may involve removing the joint surfaces of one or more of the femur, tibia, or patella bones in the medial, lateral, or patellofemoral compartments. A partial knee replacement may include replacing one or more surfaces of the upper tibia, the shin bone, and the lower femur, including the articular surface, the medial condyle, or the lateral condyle. A partial knee replacement may also include removing and replacing the inner or underside surface of the patella, also called the knee cap. A total knee replacement typically involves removal and replacement of the lower surface or distal portion of the femur, including the medial and lateral condyles; replacement of the upper surface or proximal portion of the tibia, including the medial and lateral condyles; and replacement of the inner or underside surface of the patella.
In total knee replacement, the removed bone and anatomy is typically replaced with a prosthesis. The removed parts of the femur are replaced with a femoral component, the removed parts of the tibia are replaced with a tibial component, and the surface of the patella is replaced with a patellar component. A polymer spacer is usually placed between the femoral and tibial components as an articulating surface to facilitate smooth movement between the surfaces of the components.
One concern during the bone removal stage of a knee replacement surgery is that the surgeon may not make the correct cuts to the bones which may result in malaligned prosthesis and a poorly functioning knee replacement. Therefore, accurate removal and resurfacing of the knee bones is an important part of a knee replacement surgery. Surgeons may use cutting guides and cutting blocks to assist in the cutting or sectioning of the knee bones.
Another concern is that a surgeon may place a final prosthetic that is either too small or too large for a patient's bone. Both improper bone cuts and improper sized implants may lead to untoward pain, early wear, or early loosening of prostheses that may result in a secondary unnecessary surgery.
With the assistance of computer generated data derived from CT, MRI, or other scans, such as X-rays, surgeons can more effectively determine proper alignment and positioning of the knee prosthetics in a patient through 3D modeling and rendering. Some surgeons use guides or generic extramedullary or intramedullary cutting guides during surgery in an attempt to properly place the prosthetics; however, accuracy and simplicity of existing devices and methods remain limited due to a variety of factors.